Apparatus for the solvent extraction of solids



Oct. 18, 1966 K. szAsz ETAL 3,279,890

APPARATUS FOR THE SOLVENT EXTRACTION OF SOLIDS Filed May 14, 1963 I I KALMAN SZASZ ISITVAN TAKACS JANOS FARKAS INVENTORS United States Patent 3,279,890 APPARATUS FOR THE SOLVENT EXTRACTION OF SOLIDS Kalman Szasz, Istvan Takacs, and Janos Farkas, Budapest Hungary, assiguors to Gedeon Richter A.G., Budapest, Hungary t 1 Filed May 14, 1963, Ser. No. 280,220

3 Claims. (Cl. 23-270) The. invention relates to an apparatus for the solvent extraction of solids, especially specimens of botanicals and other raw materials which have a low content of effective and extractable agents, i.e., between some hundredths and some tenths of ore percent, and where the sensitivity of the agent against chemical influences requires the use of an organic solvent in which the solubility of the agent is relatively low. Since the organic solvents necessarily employed under these conditions have a low diifusion coefiicient, the specimens are cut up or ground into granules which are smaller than 1 mm. Furthermore, with the apparatus known heretofore, the treatment time Was increased or the path length of the extraction lengthened. As a consequence of these conditions, the intimate contact between the effective agent or principle and solvent and, consequently, a perfect dissolution will be secured.

In periodic counter current systems, e.g. in diffusion batteries or equipment applying Ithrough flow of solvent after spraying, total extraction is hardly or not at all possible, because of the poor solvent-permeability of the I,

solids caused by the fine grinding. In these systems perfect exltraction is further impeded by the fact that after feeding, during the extraction or spraying the solid -is in a state of rest; in the course of spraying, channelizawhich channels the solvent or dilute solution might escape, being in contact only with a small proportion of the solid. A significant part of the solid is thus not extracted.

Indirect or, recently, direct vibrating of the two-component or two-phase system has already been proposed for improving 'the extraction. It has been found that a terial to be extracted, the holes or bores of the filter disks conveyed by the endless conveyor in the U-shaped tube are made very small-sized, to prevent undesirable passage of the solid. Such small holes exert a considerable throttling action, so that the path, or the time of the extraction, are lengthened, and the number of vibrators to be applied according to the invention is also increased, since the eifect of said vibrators covers a limited section only. 1

It was surprisingly found however, that holes with a diameter surpassing by 30 to 50 times the average dimension (diameter) of the granules of the ground solid, may be applied without endangering the uniformity and continuity of movement of the ground material. In this way the solvent permeability of the solid is highly increased and the number of the necessary vibrators can be minimized. It has been established that the reason for ,tion occurs in the solid mass of fine powder, through.

3,279,890 Patented Oct. 18, 1966 ice this remarkable phenomenon is the fact that the ground vegetal malterial (botanicals) contains vegetable fibres long enough to prevent elfectively the passage of the matter, up to certain hitherto unknown limits.

In conventional extractors, introduction of the solvent into the extraction cycle occurred at a point below the outlet of the extracted solid. On the olther hand, this outlet is necessarily situated higher than the outlet for the solution already containing the active agent, so as to gain a hydrostatic height suificient for the counter-current flow of the solvent. It would be advantageous to choose this height as great as possible, but this is limited by the fact that the return flow of the solvent entrained by the solid between the solvent inlet and the outlet of the solid must be provided for, otherwise the solvent carried away from the extraction zone by the solid would be wasted. In the case of a low content of effective agent this loss increases, since then a larger solvent quantity is necessary. To fulfill all these contradictory requirements under optimal working conditions, a compromise must be made, with the aid of which [the optimal position of the inlet for the solvent could be established by trial. Since in the mixture composed of solid and fluid phases the liquid permeability of the solid matter varies with material and solvent, the solvent inlet found most suitable for one material would perhaps not be the best for another.

In order to eliminate these defects, in accordance with 'the'prese'nt invention, three solvent inlets are arranged one above the other, permitting to choose the most suitable one for the solvent in question.

One possible embodiment of the extractor, according to the present invention is shown schematically in the sole figure of the accompanying drawing, which is a vertical section along the center line of an extraction device.

The extractor is essentially a U-shaped tube 1, the vertical branches of which are connected at their upper ends'with a horizontal tube portion; inside the extractor an endless chain 2 is arranged. The chain 2 has equispaced transversely extending filter disks 3 for conveying synchronized helical conveyor 5 at that end of the U- shaped tube at which the disks enter the extraction zone. Thus, the disks carry the solid, which is removed at the other end, through the tube to the slide 6. The solvent enters below the latter through one of the inlet pipes 7, and passes against the flow of the ground solid (countercurrent thereto); the solvent leaves in the form of a concentrated solution through the outlet tube 9 which is provided on the other branch of the tube, lower by the distance it than the solvent inlet 7. In such a way an ideal counter-current develops, in which the fine grist of solid 0 moves against and through the solvent. That quantity of the grist which is situated between two neighboring filter disks 3 is illustrated in the drawing by the hatched plug 8- To obtain a more favourable extraction rate, the U- shaped tube has a double wall 10, whereby the tube is heated between the inlet of the solid, i.e., the helical conveyor 5, and the inlet of the solvent, i.e., one of the pipes 7, while the tube may be cooled between the inlet of the solvent and the outlet of the extract, i.e., the slide 6. Extraction is improved by the heating zone, while the quantity of the solvent lost through entrainment with the drag is reduced by the cooling zone.

The loss of solvent is further diminished in the apparatus according to the invention by the fact that instead of one solvent inlet pipe 7, three are employed, among which by trial, the one best suited to the behaviour of the pair of materials (i.e., solvent and solid) is chosen. In the case represented it is supposed that the solvent is introduced through the central stub 7. In this case there is 'a hydrostatical height h available for driving over the solvent, and a tube portion of a height m is at disposal for the evaporation and return flow of the solvent from the solid.

In the system described, however, the fine grist of the solid represents a significant obstacle in the passage of the fluid. This resistance is overcome by three vibrators 11. Vibration is transmitted directly to the heterogeneous system composed of solid grist and solvent. The solvent permeability of the solid is thus considerably increased. Besides, vibrating has a powerful accelerating effect upon the extraction based on the diffusion process, i.e., penetration of the solvent into the vegetable cells, dissolution and diffusion of the efiective agent. The diffusion-accelerating effect of vibration is equivalent to the most vigorous mechanical stirring, which, however, is not realizable on a large scale.

It might be supposed, as mentioned in the introduction, that the dimension of the holes of the disks 3 conveying the solid is limited by the fine grinding necessary for the extraction of the effective agent. It has been proved by systematic experimentation that holes having diameters exceeding by as much as 30 to 50 times that of the granules are suitable thereby ensuring uniformity and continuity of the flow of the finely ground solid material. The fluid permeability of the solid is further increased by the over-dimensioned filtering holes.

Twelve taps 12, placed equidistantly along the extractor body permit simultaneous removal of samples of solid and solution simultaneously from twelve places during the balanced run of the extractor. I

The flow rate of the solid and the solvent is naturally also measurable at any time.

Determining the effective agent content of the solid and solution samples obtained during the uniform run of the extractor, and plotting these values graphically corresponding to the parameters measured at the equidistant sample-retaining places along the extraction path, two parallel or coincident parabolic curves are obtained. Proximal to the drug or extraction solution inlet, the drug contains the maximum or near maximum of effective agent; here the extract must be saturated. At the other end of the extractor, closest to the outlet of the extracted drug, that is, the inlet of the solvent, this latter must not contain any effective agent.

The hydrodynamical resistance increased by the velocity of the solid material may be counteracted by the fluid, within certain limits, if the hydrostatical level is increased between the inlet and the outlet. The possibility therefor is given by one of the solvent inlets 7, which is in every case placed higher than the outlet pipe 9 for the extract. Each of these is equipped with a level-controlling device, that is, feeding in of the solvent is controlled automatically.

What we claim is:

1. Continuous extractor for the solvent extraction of comminuted solid material, comprising:

a generally U-shaped extractor tube having a pair of upright shank portions interconnected by a bight portion at a lower part of said tube;

endless-conveyor means within said tube having a plurality of liquid-permeable filter disks spaced apart therealong and displaceable through said tube in one direction, whereby said disks run downwardly along one of said shank portions and upwardly along the other of said shank portions;

feed means at an upper part of said one of said shank portions for introducing a comminuted material to be extracted into said tube and depositing it upon said disks;

inlet means at an upper part of the other of said shank portions for introducing into said tube an extraction liquid and passing it through said tube opposite the direction of movement of said disks;

outlet means on said one of said shank portions below said feed means and below the level of said inlet means for discharging the liquid upon its extraction of said material, thereby forming a liquid head equal substantially to the vertical distance of said inlet means above said outlet means, said conveyor means having a stretch at the upper ends of said shank portion wherein said disks are diverted from said other of said shank portions to said one of said shank portions;

discharge means at the upper end of said other of said shank portions and spaced above said inlet means for discharging the extracted comminuted material from said tube; and

a plurality of vibrators each connected with one of said portions for vibrating the comminuted material displaced therethrough by said disks to facilitate the passage of said liquid through the mass of comminuted material and ensuring intimate contact between said material and said liquid.

2. An extractor as defined in claim 1 wherein said inlet means includes a plurality of inlet pipes vertically spaced along said other of said shank portions and selectively operable to introduce said liquid into said tube and correspondingly adjust said head, said comminuted material being a fibrous botanical ground to a predetermined particle size, said disks each being provided with a multiplicity of perforations having diameters between 30 and 50 times said predetermined particle size.

3. An extractor as defined in claim 1 wherein said stretch is horizontal and is enclosed by a top portion of said tube, said conveyor means further comprising a pair of guide wheels engageable with said disks and respectively disposed at the junctions between said top portion and the respective shank portions, said tube being provided along said shank portions and said bight portion at least between said outlet means and said inlet means with a multiplicity of equispaced taps for removing samples of said material and said liquid, said feed means including a helical feed screw synchronized with said conveyor means, said extractor further comprising:

heating means along at least part of said one shank portion; and

cooling means along at least part of said other shank portion and intermediate said inlet means and said discharge means, each of said shank portions and said bight portion being provided with respective vibrators individual thereto.

References Cited by the Examiner UNITED STATES PATENTS 2,273,557 2/1942 Bonotto 23-270 X 2,603,667 7 7/1952 Pankratz et al. 23-267 X 2,667,407 1/ 1954 Fenske et al. 23-310 2,731,149 1/1956 Findlay 210400 X 2,963,158 12/1960 Jung 210-384 X REUBEN FRIEDMAN, Primary Examiner.

SAMIH ZAHARNA, Examiner. 

1. CONTINUOUS EXTRACTOR FOR THE SOLVENT EXTRACTION OF COMMINUTED SOLID MATERIAL, COMPRISING: A GENERALLY U-SHAPED EXTRACTOR TUBE HAVING A PAIR OF UPRIGHT SHANK PORTIONS INTERCONNECTED BY A BIGHT PORTION AT A LOWER PART OF SAID TUBE; ENDLESS-CONVEYOR MEANS WITHIN SAID TUBE HAVING A PLURALITY OF LIQUID-PERMEABLE FILTER DISKS SPACED APART THEREALONG AND DISPLACEABLE THROUGH SAID TUBE IN ONE DIRECTION, WHEREBY SAID DISKS RUN DOWNWARDLY ALONG ONE OF SAID SHANK PORTIONS AND UPWARDLY ALONG THE OTHER OF SAID SHANK PORTIONS; FEED MEANS AT AN UPPER PART OF SAID ONE OF SAID SHANK PORTIONS FOR INTRODUCING A COMMINUTED MATERIAL TO BE EXTRACTED INT SAID TUBE AND DEPOSITING IT UPON SAID DISKS; INLET MEANS AT AN UPPER PART OF THE OTHER OF SAID SHANK PORTIONS FOR INTRODUCING INTO SAID TUBE AN EXTRACTION LIQUID AND PASSING IT YHROUGH SSID TUBE OPPOSITE THE DIRECTION OF MOVEMENT OF SAID DISKS; OUTLET MEANS ON SAID ONE OF SAID SHANK PORTIONS BELOW SAID FEED MEANS AND BELOW THE LEVEL OF SAID INLET MEANS FOR DISCHARGING THE LIQUID UPON ITS EXTRACTION OF SAID MATERIAL, THEREBY FORMING A LIQUID HEAD EQUAL SUBSTANTIALLY TO THE VERTICAL DISTANCE OF SAID INLET MEANS ABOVE SAID OUTLET MEANS, SAID CONVEYOR MEANS HAVING A STRETCH AT THE UPPER ENDS OF SAID SHANK PORTION WHEREIN SAID DISKS ARE DIVERTED FROM SAID OTHER OF SHANK PORTIONS TO SAID ONE OF SAID SHANK PORTIONS; DISCHARGE MEANS AT THE UPPER END OF SAID OTHER OF SAID SHANK PORTIONS AND SPACED ABOVE SAID INLET MEANS FOR DISCHARGING THE EXTRACTED CONNINUTED MATERIAL FROM SAID TUBE; AND A PLURALITY OF VIBRATORS EACH CONNECTED WUTG ONE OF SAID PORTIONS FOR VIBRATING THE COMMINUTED MATERIAL DISPLACED THERETHROUGH BY SAID DISKS TO FACILITATE THE PASSAGE OF SAID LIQUID THROUGH THE MASS OF COMMINUTED MATERIAL AND ENSURING INTIMATE CONTACT BETWEEN SAID MATERIAL AND SAID LIQUID 